Many luminous point of purchase or other luminous display devices based upon the use of glowing electrical discharges through inert gases, especially neon, are known. Traditionally, such glow discharge paths have been formed within cylindrical channels produced using glass tubes that are bent to form the desired character shapes. The use of channels cut in a glass plate, said plate being then sealed using additional glass plates is also known, as described in U.S. Pat. No. 4,584,501, which also teaches the use of mirrors to produce multiple reflections of the luminous characters.
U.S. Pat. No. 4,703,574 teaches the use of cross-over bores in the back plate of three sandwiched plates hermetically sealed together and having a center plate aligned with said cross-over plates to define a legend which is made to glow by an electrical discharge through neon.
U.S. Pat. No. 4,786,841 teaches the use of three sealed envelopes phosphor coated with the primary colors red, green, and blue to produce a single picture element of electrically controllable color.
U.S. Pat. No. 4,740,729 teaches the construction of a plural color discharge lamp produced by using an outer discharge tube and an inner discharge tube each discharge tube utilizing a different phosphor to produce a light of a different color.
None of these patents however teach the use of an illumination device that can be operated without the use of a voltage above domestic line voltage. Furthermore, none of these earlier inventions utilize hundreds or even thousands of electrodes as is contemplated in the current invention. Indeed, most neon signs utilize only two or three electrodes per symbol that is to be illuminated. Furthermore, none of these patents teaches the use of mixtures of phosphors having different luminosity decay curves such that the hue and chromicity of the resultant light can be controlled by varying the flicker rate of the gas discharge.
Still other devices which utilize neon glow discharges are known and have been utilized for a variety of discharge panel applications. Such applications, however, have typically utilized the generation of charges, both ions and electrons, alternately storable at pairs of opposing discrete points or areas on a pair of dielectric surfaces backed by conductors to a voltage source as is taught by Nolan in U.S. Pat. No. 4,723,093. In this way it is possible to utilize addressable matrices of electrodes such that a truly vast number of illumination points is available. In such devices, however, the total illumination intensity is limited by the presence of the interposed dielectric layer and thus the luminescent intensity of the display produced is low and is not suitable for many advertising or other illumination purposes. Nolan does not teach the use of controlled mixtures of luminescent hosphors of different luminescent time decay curves to produce light of controllable hue and chromicity.
The following drawings illustrate how the objects of the present invention are to be accomplished.